Well, in war thunder they modeled it with 75mm (
http://wiki.warthunder.com/index.php...r_T34_Calliope) and they are very historically accurate. Also, I cannot find a picture of a Calliope with a 105mm nor any mention of the rockets being mounted on the 105 sherman. Every picture ive ever seen is with a 75mm sherman. Maybe not solid info, but all the info I can muster.